Question 1061812: 2^2x +21=10(2^x)
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! 2^2x +21=10(2^x)
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2^(2x) - 10*2^x +21 = 0
(2^x - 3)*(2^x - 7) = 0
********* Sub u for 2^x to make it clearer.
u^2 - 10u + 21 = 0
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2^x - 3 = 0
2^x = 3
x*log(2) = log(3)
x = log(3)/log(2) =~ 1.585
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2^x = 7
Do the same way.
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